(1) Field
The present inventions relate generally to an apparatus for producing a shifted angle fabric and, more particularly, to an apparatus and method for producing a shifted angle fabric having balanced crimp and the product produced thereby.
(2) Related Art
Conventional woven fabrics are produced with lengthwise warp yarns and crosswise weft yarns interlaced at an angle of 90 degrees. For some applications, including power transmission belts, tires, and hoses, it is useful to rotate the fabric by cutting diagonally and turning the cut panels so that the warp and weft yarns are disposed at ±45 degrees relative to the longitudinal axis of the product. This biased fabric will exhibit increased elongation under load compared to the original fabric orientation.
It has previously been found that, prior to biasing, the elongation properties can be further increased by altering the angle of the warp/weft yarns from the as-woven 90/90 degrees (e.g. 110/80 degrees or 120/70 degrees) by shifting the weft yarn while keeping the warp yarn in its original straight and parallel orientation. The shifted angle fabric is then cut and turned using the conventional biasing techniques so that the obtuse angle is oriented in the machine direction, thereby increasing the elongation properties of the fabric when placed under load. This shifting process has been conducted using various methods so that one selvage of the woven fabric is advanced relative to the opposite selvage.
One commonly used method involves passing wetted-out woven fabric over one or more pairs of angled and tapered rollers followed by drying the fabric on a conventional clip-tenter frame through a dryer. This method typically produces a shifted angle fabric with substantially unbalanced crimp and elongation properties in the warp yarn direction compared to the weft yarn direction. Additionally, shifted angle fabric produced by this method will exhibit an undesirable variation in warp yarn crimp and elongation when comparing measurements taken at different points across the width of the fabric, and variation in warp-weft crossover angle measured at different points across the width of the fabric.
Another method involves use of a specially built tenter frame and dryer with rails arranged in a laterally curved path. The equipment used in this method must be custom made at considerable expense, and cannot be used for processing other types of fabrics.
Thus, there remains a need for a new and improved apparatus which is adapted to produce a shifted angle fabric while, at the same time, producing balanced crimp and the product produced thereby.